铈铁复合氧化物的结构特征及其催化应用

Structural Features of Ce-Fe Mixed Oxide and Its Applications in Catalysis

氧化铈(CeO2)是一种重要的催化材料,在环境催化和催化氧化等诸多领域表现出了出色的催化性能。将其他金属离子引入氧化铈晶格通过电荷平衡原理诱导产生丰富的氧空位,是提高氧化铈催化性能的有效方法。当Fe3+进入CeO2晶格时,由于其离子半径较小,可同时形成取代和间隙两类固溶体,取代与间隙位Fe3+的摩尔比决定着氧空位的浓度,这使铈铁复合氧化物上的氧空位浓度极具调变性。另外,由于氧化铁本身亦对某些反应具有催化活性,游离的氧化铁与氧化铈颗粒间形成的特殊界面也表现出了优异的催化特性。铈铁间多重的协同作用使这类复合氧化物具有较高的研究和使用价值。本文介绍了铁离子在氧化铈中的固溶度和氧空位调变性等铈铁复合氧化物的结构特点,探讨了该材料的结构对其制备条件的敏感性,概述了其在催化领域的应用,并讨论了铈铁交互作用在催化过程中的作用。结合本课题组的一些研究成果,指出了铈铁材料尚未解决的一些关键问题和可能的研究方向。

CeO2 is one of the most interesting oxides in the fields of catalysis （e. g. , environmental catalysis and catalytic oxidation） because of the rapid formation and elimination of oxygen vacancies. The performance of CeO2 can be strongly improved under doping. Synthesis of ceria-based solid solutions with controllable concentrations of oxygen vacancies is of great fundamental significance. Since the properties of the ceria-based solid solutions are affected by the dopant size and valence （lower valence ions in ceria could lower the activation energy for oxygen migration, and smaller ions enhance the oxygen storage capacity）, introducing cations with smaller size and lower valence as compared to Ce4＋ （e. g. , Fe3＋ ） into the ceria lattice owns considerable scientific and technological value. It has been observed a series of interesting phenomena in the structure and catalytic applications of CeO2-Fe2O3 solid solution. Moreover, the interface between CeO2 and Fe2O3 particles （e. g. , Ce-O- Fe bridges） also reveals special features in catalysis. In this review, the structural features of Ce-Fe mixed oxides, including the solubility of Fe ions in ceria lattice, formation of oxygen vacancies and CeO2-Fe2O3 interaction are discussed, which are related to their activity in catalytieal applications （e. g. , purification of exhaust gases from vehicles, catalytic oxidation, hydrogen and syngas generation, and Fischer-Tropsch synthesis）. Some key issues and possible directions on the Ce-Fe mixed oxides used in catalysis are discussed.